drm/i915: Extract intel_crtc_vblank_evade_scanlines()

Pull the vblank evasion scanline calculations into their own helper
to declutter intel_pipe_update_start() a bit.
Reviewed-by: Manasi Navare <navaremanasi@chromium.org>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230901130440.2085-4-ville.syrjala@linux.intel.comReviewed-by: Mitul Golani <mitulkumar.ajitkumar.golani@intel.com>

drivers/gpu/drm/i915/display/intel_crtc.c

@@ -468,6 +468,36 @@ static int intel_mode_vblank_start(const struct drm_display_mode *mode)
 	return vblank_start;
 }
 
+static void intel_crtc_vblank_evade_scanlines(struct intel_atomic_state *state,
+					      struct intel_crtc *crtc,
+					      int *min, int *max, int *vblank_start)
+{
+	const struct intel_crtc_state *new_crtc_state =
+		intel_atomic_get_new_crtc_state(state, crtc);
+	const struct drm_display_mode *adjusted_mode = &new_crtc_state->hw.adjusted_mode;
+
+	if (new_crtc_state->vrr.enable) {
+		if (intel_vrr_is_push_sent(new_crtc_state))
+			*vblank_start = intel_vrr_vmin_vblank_start(new_crtc_state);
+		else
+			*vblank_start = intel_vrr_vmax_vblank_start(new_crtc_state);
+	} else {
+		*vblank_start = intel_mode_vblank_start(adjusted_mode);
+	}
+
+	/* FIXME needs to be calibrated sensibly */
+	*min = *vblank_start - intel_usecs_to_scanlines(adjusted_mode,
+							VBLANK_EVASION_TIME_US);
+	*max = *vblank_start - 1;
+
+	/*
+	 * M/N is double buffered on the transcoder's undelayed vblank,
+	 * so with seamless M/N we must evade both vblanks.
+	 */
+	if (new_crtc_state->seamless_m_n && intel_crtc_needs_fastset(new_crtc_state))
+		*min -= adjusted_mode->crtc_vblank_start - adjusted_mode->crtc_vdisplay;
+}
+
 /**
  * intel_pipe_update_start() - start update of a set of display registers
  * @state: the atomic state
@@ -487,7 +517,6 @@ void intel_pipe_update_start(struct intel_atomic_state *state,
 	struct drm_i915_private *dev_priv = to_i915(crtc->base.dev);
 	struct intel_crtc_state *new_crtc_state =
 		intel_atomic_get_new_crtc_state(state, crtc);
-	const struct drm_display_mode *adjusted_mode = &new_crtc_state->hw.adjusted_mode;
 	long timeout = msecs_to_jiffies_timeout(1);
 	int scanline, min, max, vblank_start;
 	wait_queue_head_t *wq = drm_crtc_vblank_waitqueue(&crtc->base);
@@ -503,27 +532,7 @@ void intel_pipe_update_start(struct intel_atomic_state *state,
 	if (intel_crtc_needs_vblank_work(new_crtc_state))
 		intel_crtc_vblank_work_init(new_crtc_state);
 
-	if (new_crtc_state->vrr.enable) {
-		if (intel_vrr_is_push_sent(new_crtc_state))
-			vblank_start = intel_vrr_vmin_vblank_start(new_crtc_state);
-		else
-			vblank_start = intel_vrr_vmax_vblank_start(new_crtc_state);
-	} else {
-		vblank_start = intel_mode_vblank_start(adjusted_mode);
-	}
-
-	/* FIXME needs to be calibrated sensibly */
-	min = vblank_start - intel_usecs_to_scanlines(adjusted_mode,
-						      VBLANK_EVASION_TIME_US);
-	max = vblank_start - 1;
-
-	/*
-	 * M/N is double buffered on the transcoder's undelayed vblank,
-	 * so with seamless M/N we must evade both vblanks.
-	 */
-	if (new_crtc_state->seamless_m_n && intel_crtc_needs_fastset(new_crtc_state))
-		min -= adjusted_mode->crtc_vblank_start - adjusted_mode->crtc_vdisplay;
-
+	intel_crtc_vblank_evade_scanlines(state, crtc, &min, &max, &vblank_start);
 	if (min <= 0 || max <= 0)
 		goto irq_disable;